Hot reversing strip mill method and apparatus

ABSTRACT

THE DISCLOSURE OF THIS APPLICATION RELATES TO A ROLLING MILL AND, MORE PARTICULARLY, TO A HOT METALLIC STRIP REVERSING MILL OF THE TYPE KNOWN AS A STECKEL MILL. THERE IS PROVIDED A 4-HIGH MILL ON EITHER SIDE OF WHICH THERE ARE LOCATED COILING FURNACES AND REELS FOR RECEIVING THE STRIP AS IT IS PASSED TO AND FROM THE MILL. THE MILL IS ALSO PROVIDED WITH A QUICK ROLL CHANGING DEVICE IN WHICH CONNECTION THE NOVEL METHOD IS DISCLOSED FOR EMPLOYING THE FURNACE TO HOLD THE STRIP IN THE FURNACE WHILE THE WORK   ROLLS ARE BEING CHANGED FROM A ROUGHING SET TO A FINSIHING SET OF WORK ROLLS.

Oct. 19, 1971 J. R. ADAIR ETAL 3,613,426

HOT REVERSING STRIP MILL METHOD AND APPARATUS Filed Oct. 14, 1969 2 Sheets-Sheet 1 ATTORNEY HOT REVERSING STRIP MILL METHOD AND APPARATUS Filed Oct. 14. 1969 Oct. 19, 1971 J. R. ADAIR EIAL ZSheetS-Sheet 2 1| INVENTORS.

mes/2 404? MDEUSZMB/MS/EW/CZ- United States Patent O US. Cl. 72-202 Claims ABSTRACT OF THE DISCLOSURE The disclosure of this application relates to a rolling mill and, more particularly, to a hot metallic strip re versing mill of the type known as a Steckel Mill. There is provided a 4-high mill on either side of which there are located coiling furnaces and reels for receiving the strip as it is passed to and from the mill. The mill is also provided with a quick roll changing device in which connection the novel method is disclosed for employing the furnace to hold the strip in the furnace while the work rolls are being changed from a roughing set to a finishing set of work rolls.

Present-day mills of the Steckel type usually employ a roughing mill where the carbon or stainless steel slab is reduced to a thickness of approximately of an inch and then is sent to a separate finishing mill having coilers and reels at either side for receiving the strip and preventing it from cooling during the rolling process. The capital expense of such an arrangement is substantially high even though the type of mill described is usually designed to meet a low economy operation.

The present invention provides a novel method and apparatus for operating a Steckel type mill in which only one mill stand is employed which serves both the function of the roughing stand and the finishing stand of the previous arrangement. This method and apparatus comprise the employment of a set of work rolls designed to perform the roughing passes on a workpiece fed to and from the mill, the employment of coilers for coiling the reduced workpiece in one of two furnaces and holding it in the furnace while the roughing work rolls are rapidly removed and replaced by finishing work rolls by a quick roll changing device, after which the workpiece is uncoiled from the furnace and the finish passing is performed by the finishing work rolls, during which time the furnaces may again be employed to hold the heat in the workpiece.

These features and others may be better understood when the following description is read along with the accompanying drawings, of which:

FIG. 1 is an elevational view of a mill arrangement for carrying out the present method and incorporating the novel apparatus, and

FIG. 2 is a partial plan view of the apparatus shown in FIG. 1.

With reference to FIGS. 1 and 2, there is illustrated a rolling mill 10 which includes a pair of spaced-apart housings 11 and 12, each housing receiving a mill screw 13 which is rotated by a drive arrangement 14, the screws 13 engaging upper backup chocks 15 which rotatably support a backup roll 16 received in the housings 11 and 12. At the lower part of the mill, a similar backup roll chock 17 is provided which rotatably supports a lower backup roll 18. Each backup roll is adapted to support upper and lower work rolls 19 and 21 which are received in bearing chocks 22 and 23, respectively, As will be 3,613,426 Patented Oct. 19, 1971 "ice appreciated, the above-described members of the rolling mill are well-known components in the art, as are other illustrated components thereof, and for which reason they will not be specifically identified, since this is not necessary to understand the present invention. It will be noted, however, as illustrated in FIG. 2, that the work rolls 19 and 21 are adapted to be driven by spindles, one of which is shown at 24, by a drive 25. The operation data of a Steckel hot mill is also well known as exemplified by an article entitled The Reversing Hot Strip Mill Its Place in the Steel Industry, written by David Lyle, appearing in the Iron and Steel Yearbook, April 1956, pages 283 through 290.

Illustrated in FIG. 1, on either side of the mill 10 there is provided a furnace 26 which may follow a number of well-known designs. The furnaces which are identified each comprise an outer frame 27, an inner refractory chamber 28 onto which there is mounted a rotatable reel 29 which is adapted to receive through a slot 31 the front end of a strip for winding the strip around the reel. Since both sides of the mill are identical with respect to the coiler assembly, from this point on only the side at the left of the mill illustrated in FIG. 1 will be described.

The coiler arrangement also comprises a tailing roll 32 which is pivotally mounted on the stand 33 and pivoted by a linkage-cylinder arangement 34. To the right of the tailing roll 32 there is provided a tiltable apron 35 which is pivoted at 36, which actually is coincident with the lower pinch roll 37. The apron, which serves as part of the horizontal table, in one position is pivoted to a raised position to serve as a holding roller for the reel by the means of a linkage-cylinder arrangement 38. The pinch roll 37, previously mentioned, cooperates with an upper pinch roll 39 which is received in a pinch roll frame 41, the upper roll being adapted to be raised and lowered through a piston cylinder assembly 42. The pinch roll frame 41 also carries a horizontally arranged stripper knife 43 which is carried in a guide 44 mounted on a pinch roll and actuated by a piston cylinder assembly 45. Between the pinch roll and mill there is provided a roller table 46.

In now referring particularly to FIG. 2, it will be noted that to one side of the mill 10 a side-shifting roll changing rig mechanism 47 is provided, which mechanism consists of two pairs of transverse extending tracks 48 and 49 which are arranged in a parallel relationship and serve as two side-by-side supporting areas for receiving two pairs of interrelated or nested work rolls, one pair being shown in FIG. 2. The tracks are adapted to be moved so as to line up with the windows of the mill so that the tracks 48 can receive a set of work rolls from the mill, for example, the roughing rolls, while the other set of tracks supports a second set of rolls and can be positioned in front of the windows once the first set of rolls is shifted. This side shifting is performed by means of a third pair of tracks 51 and 52 over which an upper platform 53 of a shifting car that carries the tracks 48 and 49 rides and is moved by a piston cylinder assembly 54.

At the drive side of the mill, it will be noted, there is provided a piston cylinder assembly 55 having a pusher ram 56 adapted to engage the work roll chocks while in the mill and exert a force through operation of the cylinder to eject them from the mill onto the waiting pair of tracks 48. Reverse operation of the piston cylinder assembly 55 will transport a replacement pair of rolls from the roll changing rig to the mill after the pusher ram 56 is caused to engage the chocks of the new set of rolls.

Referring now to the novel method of rolling disclosed in this application, let it be assumed that a stainless steel slab is to be received from the left of the mill illustrated in FIG. 1, in which connection it will be noted that the mill is set up with a set of roughing work rolls 19 and 21, preferably of a steel composition. The slab, measuring 6" x 52" x 20 having a temperature of approximately 2200 F., is advanced over the roller table 46 into the mill 10 and issues therefrom to the right-hand side of the mill. After a given number of reverse passes, say, for example, seven to nine, the slab is reduced without being coiled to a thickness of approximately of an inch. On the last pass through the mill (let us assume that it is a pass going in the direction of the furnace 26), the strip having a temperature of approximately 1900 F., is coiled in the furnace as it leaves the mill 28, the furnace temperature being of the order of 1900 to 1950 F. In doing this, the pinch roll 39 is lowered by the cylinder 42 so as to grip the strip at the same time the cylinder 38 is operated to raise the lifting table 35, thereby conveying the leading end of the strip into the slot 31 of the reel 29 and upon the rotation of the reel, the remainder of the strip is wound on the periphery of the reel.

As the coil is completed, the tailing roll 32 is brought into engagement with the outer periphery of the coil to hold the end tight against the body at the same time the outer convolution is engaged by the upper roller of the lifting table 35. While this is happening, the roughing mill work rolls are quickly retracted from the mill by virtue of the piston cylinder assembly 55 onto the pair of tracks 48. After this, the cylinder 54 is operated to shift the roughing work rolls out from in front of the mill and to position the finishing work rolls, which preferably are of an iron composition, in the position for engagement by the rams 56. Ultimately, operation of the cylinder 55 brings the new rolls into the mill stand. The operation of changing the rolls is designed to take approximately three minutes.

During the time the furnace 24 is holding the temperature of the coil at approximately 1800 F. during roll changing, the roll 29 is rotated very slowly clockwise so that when the strip is to be re-fed to the mill the rotation of the reel reversed and the stripper 42 is brought into engagement with the leading end of the strip to peel it away from the body and send it onto the tilting table 35, which has been lowered to a horizontal position. At this time, the roller 32 is being driven at a slightly higher speed which tends to hold the coil tight and drive the strip on the guideway and through the open pinch rolls 37 and 39, after which the upper roll 34 is brought into engagement with the strip to urge it into the mill. As this occurs, the tailing roll 32 is lowered out of position and the speed of the reel 29 is raised to uncoil the strip. The furnace 27 on the other side of the mill will receive the strip after the first finishing pass, and the operation is continued until between two to four finishing passes are taken on the strip, the temperature of which will be approximately 1550 to 1600 F.

Thus, the present invention allows one to obtain the best possible finish for the strip by using a different set of rolls for the finishing passes than is employed for the roughing passes. As noted before, it was customary to provide two rolling mill stands for accomplishing this Purpose. According to the present invention, the employment of the furnace as a holding furnace in construction and the quick roll changing rig which allows the roughing work rolls to be removed and replaced by a finishing set of work rolls, all within a very short time (on the order of three to five minutes) and without any detrimental effect, presents an arrangement that gives maximum production at a considerable reduction in capital expense.

It will be appreciated by those familiar with the art that many different forms of the present method and apparatus can be employed without departing from its spirit, in which a turntable could be substituted for the side shifter roll changing device and a different furnace arrangement may be provided.

In accordance with the provisions of the patent statutes, we have explained the principle and operation of our invention and have illustrated and described what we consider to represent the best embodiment thereof.

We claim:

1. In a method of hot rolling a metallic workpiece comprising the steps of:

first placing a first set of reducing rolls in a rolling mill,

subjecting the workpiece to a number of roughing passes by said first set or rolls,

coiling the workpiece after the last roughing pass,

holding said workpiece in its coiled form in a manner to prevent loss of heat below the rolling temperature of the workpiece,

during said holding step removing said first set of rolls from said mill and replacing them with a second set of reducing rolls, and

unwinding said workpiece from said coiled form and subjecting the workpiece to at least one finishing pass by said second set of reducing rolls.

2. In a method of operating a hot rolling mill having coil furnaces on the entry and delivery sides of the mill, comprising the steps of placing a first set of reducing rolls in said rolling mill,

employing said first set of rolls to reduce a slab to a strip of a thickness conducive to coiling,

coiling said strip in one of said furnaces to maintain its temperature at the rolling temperature,

while said strip is in said furnace, removing said first set of reducing rolls from said mill and replacing them with a second set of reducing rolls,

uncoiling said strip into said mill and subjecting the strip to more than one finishing pass by said second set of rolls, and

coiling said strip in said furnace after all-but-the-last finishing pass.

3. In a method of operating a mill according to claim 2, the additional step of:

causing the strip to be slowly rotated while in said furnace during the time the rolls are being removed and replaced.

4. In combination with a rolling mill adapted to perform a series of roughing and finishing reduction passes on a workpiece,

furnaces arranged on either side of said mill, strip coilers arranged in said furnaces adapted to coil strip received in said furnaces, means including drive means for causing the workpiece to be reduced when said mill has inserted in it a set of roughing rolls, means for causing said workpiece after reduction by said roughing rolls to be advanced to one of said furnaces for coiling therein, a roll changing apparatus at one side of said mill, said apparatus including a support area for receiving a set of roughing reducing rolls from said mill, said apparatus also including a second support area for receiving a set of finishing reducing rolls for insertion into said mill, means for quickly moving said roughing reducing rolls out of said mill onto said first support area and moving said finishing reducing rolls from said second support area into said mill, means for advancing said workpiece to said mill, and said means including drive means causing said finishing reducing rolls to further reduce said workpiece. 5. In combination with a rolling mill according to claim 4 wherein said roughing rolls perform a number of roughin g passes and with respect to said reduction by said roughing rolls said workpiece is coiled only after the last roughing pass.

6. In combination with a rolling mill according to claim 4 wherein said means for advancing said workpiece to said mill comprises a mill table, and

a pinch roll unit arranged between said one furnace and said mill for advancing the workpiece from said mill to said furnace and from said furnace to said mill.

7. In combination with a rolling mill according to claim 4 wherein one of said strip coilers include driving means for effecting the coiling and uncoiling of the strip.

8. In combination with a rolling mill according to claim 7 wherein said driving means includes a means for causing said coiler to slowly rotate a coil during the period when said rolls are being changed.

9. In combination with a rolling mill according to claim 7 including a tailing roll,

means for moving said tailing roll into engagement with a coil While said coil is being slowly rotated and upon the strip being advanced from the furnace to said mill. 10. In combination with a rolling mill according to claim 4 in which said support areas are formed by separate platforms,

means for supporting said platforms in a manner that the platforms are shiftable into and out of the roll changing position relative to said mill, and means for shifting in unison said platforms.

References Cited UNITED STATES PATENTS 4/ 1875 Wilmot 72-202 2/ 1905 Kent 72-202 1/ 1937 Trinks 72-202 6/ 1939 Manion 72-202 7/1967 King 72-250 US. Cl. X.R. 

